Screenshot of Milwaukee’s “greenness” measures vs. average home value by neighborhood. Source: City Nature

Bob Lalasz is director of science communications at The Nature Conservancy.

The evidence keeps sprouting up like daffodils: Experiencing nature is good for us — physically, emotionally, cognitively. (Check out this new study on how a walk in the park can reduce brain fatigue.) But as the world becomes ever more urbanized, which urbanites have enough access to nature to reap these benefits…and how can we make that access more equitable?

Enter City Nature — a new project from Stanford University that maps the “greenness” and “paved-ness” of more than 2,500 neighborhoods in 34 U.S. cities (as determined by the shade of remotely sensed pixels) and then lays over that demographic data such as ethnic diversity and average home value as well as access to parks to produce portraits of American urban nature — who lacks it, who has it in abundance, and how those disparities match up with individual city plans and visions.

Those disparities are wide, according to Jon Christensen, an environmental historian who is one of City Nature’s two principal investigators and who teaches in UCLA’s History Department and Institute of the Environment and Sustainability. The hope, says Christensen, is that urban planners and activists can use City Nature’s data to eventually pinpoint the neighborhoods that have the greatest “nature need” — and take action.

But City Nature’s data also holds surprises — including how much urban nature in the United States has happened in spite of central planning, and how little impact great landscape architects such as Frederick Olmsted have had on that development. I caught up with Christensen to learn more:

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City Nature has a project called “Naturehoods” that measures neighborhood proximity to parks as well as neighborhood levels of “greenness” — which includes plants in backyards, parkways, street tree canopies. What disparities are you finding between parks and greenness across the United States? And does having a park nearby always mean you have “access” to greenness?

JON CHRISTENSEN: Parks don’t seem to be distributed in U.S. cities in a way that is biased towards any particular class. That’s partly a historical artifact of the way the cities have developed and the flight to the suburbs — there are lots of parks throughout cities.

But greenness or unpaved spaces tend to not be evenly distributed. There is a tendency — although it’s not uniform — that greener parts of cities tend to be wealthier neighborhoods with higher per-capita income and higher percentages of owner-occupied homes. That doesn’t mean that wealthy people live only in green parts of town — they can choose to live wherever they want, so they are often found in a lot of different neighborhoods and increasingly, we know, back in dense downtowns where there is often less green space.

But the greenest parts of cities often seem to be areas where people have big lots, backyards, lots of trees, nearby open space, and expensive homes. An economist might say these homeowners have made a trade-off. As one person I talked to here in L.A. told me, she doesn’t need a park, she has a big backyard. She’s only been to the local park once in decades. By contrast, the least green parts of town often seem to be home to people with lower incomes and less valuable property. They might have parks, but those parks may be more neglected, run down, more paved over to make maintenance easier for cash-strapped city park agencies, and there are fewer trees and smaller backyards, if any, and less open space around.

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